Nocturia is a lower urinary tract symptom defined as “the complaint that the individual has to wake at night one or more times to void” (Neurourol Urodyn 2002; 21: 167-178). Nocturia prevalence increases with age (J Urol 2010; 184: 440-446), and major patients with nocturia are older adults. It impairs quality of life (QOL) in that it disrupts sleep (Eur Urol 2010; 57: 488-498) and increases risk of fracture. Causes of nocturia are global polyuria, nocturnal polyuria, reduced bladder capacity, and sleep disorders, but in many patients nocturia is considered to be multifactorial (Eur Urol 2012; 62: 877-890). Nocturnal polyuria is defined as nocturnal urine volume greater than 33% of the 24-hour urine volume and is present in about 80% of the patients with nocturia (J Urol 2011; 186: 1358-1363).
Arginine-vasopressin (hereinafter, abbreviated as AVP) is an antidiuretic hormone that is a peptide consisting of nine amino acids, and is biosynthesized and secreted in the hypothalamic-pituitary gland axis. AVP receptors are classified into three subtypes: V1a, V1b, and V2. Known major pharmacological actions of AVP in the periphery are vasoconstriction through the Via receptor, and antidiuresis through the V2 receptor. AVP acts on the renal tubules to promote renal water reabsorption, decreasing the urine volume. For this reason, decreased nocturnal AVP secretion with age is assumed to be a cause of increased nocturnal urine volume (J Int Med 1991; 229: 131-134, BJU Int 2004; 94: 571-575).
Stimulation of the V2 receptor is expected to improve nocturia. Desmopressin (hereinafter, abbreviated as dDAVP) is a selective V2 receptor agonist used for treating patients with nocturia, and is reported to decrease nocturnal urine volume and the number of nocturnal voids, resulting in an increased duration of initial undisturbed sleep (J Urol 2013; 190: 958-964, and J Urol 2013; 190: 965-972). Unfortunately, V2 receptor agonists theoretically induce fluid retention and increase risks of hyponatremia. It is reported that V2 receptor agonists should be administered with caution and monitoring of serum sodium level to older adults who are the majority of patients with nocturia (Neurourol Urodyn 2004; 23: 302-305).
Placental leucine aminopeptidase (hereinafter, abbreviated as P-LAP) is an enzyme that degrades L-leucine-β-naphthylamide, oxytocin and AVP (Arch Biochem Biophys 1992; 292: 388-392), and was cloned as an aminopeptidase by Rogi et al. in year 1996 (J Biol Chem 1996; 271: 56-61). The insulin-regulated aminopeptidase (hereinafter, abbreviated as IRAP) cloned by Keller et al. from rat epididymal fat pads has homology of 87% to human P-LAP. The IRAP is subsequently suggested to be an aminopeptidase that cleaves AVP and reported to be a rat homolog of human P-LAP (J Biol Chem 1995; 270: 23612-23618, Am J Physiol Endocrinol Metab 2007; 293: E1092-E1102). Angiotensin IV (AT4) receptor isolated from bovine adrenal is also suggested to be an IRAP as a result of biochemical and pharmacological studies (J Biol Chem 2001; 276: 48623-48626).
Experiments using P-LAP knockout mice indicate that administration of AVP in wild type mice and P-LAP knockout mice results in much reduction of 24-h urine volume in P-LAP knockout mice, although no significant difference is observed in the 24-h urine volume between the wild type and P-LAP knockout mice. It suggests the possible involvement of P-LAP in regulation of the urine volume through degradation of AVP (NPL 1).
Compounds represented by Formula (A) below are reported to be IRAP inhibitors useful as a therapeutic agent for dementia and diabetes, and the like (PTLs 1 and 2).
wherein X is O, NR′ or S, and other symbols are defined as in PTLs 1 and 2.
Tripeptide analogs of AT4 with 13- to 14-membered ring structure exhibits excellent IRAP inhibitory activity (NPL 2).
However, no antidiuretic agent or therapeutic agents for nocturia based on a mechanism mediated by P-LAP (or IRAP) has been reported.
Under such circumstances, there exists need for a safe antidiuretic agent that is suitable for treating nocturia.